1. Field of the Invention
This invention relates to the field of solid state electronics, and particularly to the field of solid state arrays of photodetectors.
2. Description of the Prior Art
Prior art photodetector arrays are based on the use of photodiodes (p-n junctions). The array of photodiodes is coupled to a silicon chargecoupled device (CCD) by direct injection or by modulation through the gate of a field effect transistor (FET).
The unit cell size of such prior art devices is limited to a minimum of about 4.times.4 mil.sup.2.
For prior art devices utilizing gate modulation coupling, the photodiodes' anode potential is determined, for small diode currents, by the threshold voltage of the top gate FET. Since the threshold voltage can vary appreciably (by as much as 50 mV) along the focal plane, the photodiode bias changes from individual photodiode to individual photodiode. Such change in bias causes a significant amount of fixed-pattern noise in prior art photodetector arrays.
Prior art devices utilizing direct injection are handicapped by low injection efficiency.
Photodetector arrays of capacitive detectors have not been used satisfactorily in place of photodiode detectors because of a lack of a suitable means for processing the capacitively couple voltage output of the capacitive detectors.